The height of the parallelogram is half its base. If its area is $200 {\mathrm{cm}}^2$, find its height and base.

The base of a triangular field is twice its altitude. If the cost of levelling the field, at the rate of $₹10 \mathrm{per} {\mathrm{m}}^2$ is $₹4000$, find its base and altitude.                                                                                             

The area of the shaded portion is $k {\mathrm{cm}}^2$. Find the value of $k$. $\left[\text{Take} \mathrm{\pi }=\frac{22}{7}\right]$

A quarter circle is drawn at each corner of the square. The area of the shaded portion is $k {\mathrm{m}}^2$. Find the value of $k$.

Note: Use $\mathrm{pi}=3.14$.